1. Field of the Invention
This invention is directed to a process of making meta-chlorobenzoyl chloride in improved yields. Meta-chlorobenzoyl chloride is a highly useful starting material in the production of certain herbicides, i.e. halophenoxy nitrobenzoates. The process of this invention, therefore, can be utilized in making the halophenoxybenzoic acid herbicides disclosed by U.S. Pat. No. 3,652,645.
2. Description of the Prior Art
E. Hope and G. C. Reily reported, in the Journal of the Chemical Society, Vol. 121, page 2,510, 1922, the chlorination of benzoyl chloride. However, no solvents were used and the catalyst consisted of ferric chloride only, i.e. benzoyl chloride was chlorinated with anhydrous ferric chloride as the only catalyst. The yield of monochlorobenzoyl chlorides was 76% at 87% benzoyl chloride conversion. The isomer distribution of the monochlorinated fraction was 83.5% meta-, 14.5% ortho- and 2% para-chlorobenzoyl chloride.
Other methods that have been described in the prior art for the preparation of this chloride generally start with materials that already contain nuclear chloride, as for example, the conversion of chlorobenzaldlhyde to monochlorobenzoyl chloride using carbon tetrachloride as solvent. In such processes, the monochlorinated form produced contain meta and disproportionate amounts of ortho- and para-fractions.
U.S. Pat. No. 3,816,526 shows improvement in the chlorination of benzoyl chloride when the reaction is carried out in a chlorinated hydrocarbon solvent; the improvement being selectivity to meta-chlorobenzoyl chloride. For example, at 85% benzoyl chloride conversion, 80% monochlorobenzoyl chlorides and 5% dichlorobenzoyl chlorides were obtained. The isomer distribution of the monochlorinated fraction was 91.5% meta-, 6.5% ortho-, and 2% para-chlorobenzoyl chlorides.
U.S. Pat. No. 2,890,243 discloses preparation of polychlorobenzoic acids by chlorinating benzoyl chloride at temperatures from 100.degree.-150.degree. C or higher in the presence of ferric chlorideiodine catalyst and in the absence of a solvent to produce a mixture of polychlorobenzoyl chloride.
Applicant, however, has discovered a catalytic process wherein the desired meta-isomer of monochlorobenzoyl chloride is preferentially obtained in high yield without the use of high temperatures or solvent.